The present invention relates to a manually guided or portable implement having a motor unit and a tool unit driven by the motor unit.
Manually guided implements, such as power tillers, brushcutters, trimmers, pruners, chain saws or the like, must be easy to handle. For this purpose, a compact construction and a low weight are desirable. To nevertheless be able to achieve a high output with a small and lightweight combustion engine, it is necessary, among other features, to have a high operational speed. During operation, this results in a high generation of noise, which must not exceed a certain limiting value.
As measures to limit the generation of noise, in addition to mufflers and other means, speed regulators are also known that when low load is present at the driven tool prevent an excessive speeding-up of the internal combustion engine. During operation, the tool that is driven by the internal combustion engine is subjected to fluctuating loads, which cannot always be absorbed by the user by means of an adaptation of the throttle position. In particular at full throttle, and suddenly declining operational load, the speed regulator prevents an excessive increase in speed. In addition to limiting the generation of noise, the tool and the drive train are also protected against overloading caused by speed.
To limit or regulate the speed, various arrangements are known according to which an adjustment of the choke valve, the actuation of a speed-regulating valve in the carburetor, an ignition influence or the like is provided. To the extent that such a speed regulator interferes in the operation of the internal combustion engine, the result is a disadvantageous influence upon the mixture or exhaust gas formation as well as upon the running conditions of the internal combustion engine. For different implements having different tools, different threshold speeds can be required, which necessitate an adaptation of the speed regulator to the respective implement or application thereof. A higher construction and development expenditure is associated therewith.
It is therefore an object of the present invention to further develop an implement of the aforementioned general type in such a way that a straightforward and reliable speed regulation is possible under different operating conditions.